I have just written a hugely long piece, hit Post and got no server and lost everything I'd written so here is a much simplified version.
Today I shot harbour side aperture series with the A7R and 24-70. All focal lengths, all useful apertures, several iterations. I chose the best and compared them at 24mm, 50, and 70mm with F5.6 to my archive of shots of the same scene from:
D800E with Nikkor 24-70 F2.8
Oly E-M1 with 12-40 F2.8
People who read my review of the Oly lens will know that I contentiously (but correctly, naturally!) said that at 24mm it beats the Nikon combo for a 22" print because of the Nikon's less than good enough edges. As it happens, it does so at 70mm too, though loses at 50mm. Naturally I wanted to know how the new Sony lens fares against this competition.
Results are provisional. I couldn't place the tripod exactly where I usually do (there's a boat in the way) but I do know this scene very well after thousands of shots with hundreds of lens/camera/ focal length/aperture combinations. However (I know, I know, thread useless without pictures) I won't post images now because I want to do comparison shots (in more clement climactic conditions) that will stand more as evidence than opinion.
My opinion, however, after making prints and doing at lot of pixel peeping is that if edge performance for a 22" print is paramount, the Oly still wins by a little: but overall, the Sony beats both Oly and Nikon. Much more detail and fidelity and less noise than the Oly on centre, sharper edges than the Nikon at 24mm and 70mm and, though not as good at 50mm at the edges, notably more detail on centre and much less aliasing.
It is a compromise lens. I would have preferred it to be twice the price and have much better edges even if it weighed more but overall, against the competition that I own, it is the more useful lens. Edges are treatable and are as I say just about OK at this print size, centre is very good indeed, files overall win out. It is better than I feared if not as good as I dreamed. And when it isn't good enough for the shot you want, change it for a 55mm F1.8 and beat just about anything but an Otus or medium format but at a fraction the size and weight.
Pending a lot more testing, I am tempted to think that this might become my favoured travel and walkaround lens though I do need to do some distant landscape shots...